Pressure sensitive transfer sheet



3,065,099 PRESSURE SENSITIVE TRANSFER SHEET Douglas A. Newman, GlenCove, N.Y., assignor to Columbia Ribbon and Carbon Manufacturing Co.,Inc., Glen Cove, N.Y., a corporation of New York No Drawing. Filed Oct.15, 1959, Ser. No. 846,549 4 Claims. Cl. 117-36.1)

This invention relates to a new method of preparing transfer sheets andto the novel transfer sheets prepared by this method.

In the transfer paper industry, conventional carbon paper is the mostWidely used at present. This carbon paper is manufactured by What isknown as the hot melt process in which conventional paper is coated witha hot melt of Wax and carbon black pigment which is spread in a layerover the paper foundation while still in molten condition.

This process is the most common at present even though it is recognizedthat it involves many problems. One serious problem arises from the factthat hot melt wax is very light and oily and has penetrating powers farin excess over solidified wax. Therefore, when the hot wax and pigmentis coated on paper, a large amount penetrates the paper and is notavailable for transfer purposes.

Another disadvantage resides in the cost and supervision required by theheating apparatus. The machinery is bulky and the temperature of the Waxmust be closely controlled.

Therefore, it is an object of this present invention to prepare transfermedia such as webs, strips, sheets and ribbons without the necessity ofapplying the transfer coating as a wax melt.

It is another object of the present invention to prepare transfer mediawhich do not absorb the pressure-transferable layer to any extent andtherefore have substantially all of the pressure-transferable materialavailable for transfer purposes.

It is a further object of the present invention to prepare transfermedia of the carbon paper type which are cleaner to the touch and whichpressure-release images which are more smudge-resistant than thoseheretofore known by the hot melt process.

These and other objects are accomplished by the method hereinafterdescribed.

According to the present invention it has been found that conventionalpressure-transferable waxes carrying pigment may be applied to awater-resistant base as a water dispersion rather than a hot melt. Uponevaporation of the Water there remains a pressure-transferablecomposition at the surface of the paper completely available forimaging.

It has been found important that the foundation sheet be substantiallyWater-resistant. Otherwise, of course, the foundation would beimpregnated with the water dispersion of the wax and pigment which wouldthen not be available for transfer purposes. In this regard it has beenfound that any water-resistant paper foundation may be used such asconventionally sized paper, paper treated with wet-strength agents orpaper coated with waterresistant materials such as ethyl cellulose,vinyl resin such as vinyl chloride-vinyl acetate copolymers, polyvinylacetate or polyvinyl butyral, etc. The water-resistant plasticfoundations such as cellophane, cellulose acetate, polyethyleneterephthalate (Mylar), polyvinylidene chloride (Saran), polyvinylchloride, vinyl chloride-vinyl acetate copolymer (Vinylite VYHH), andothers may also be used in place of treated paper.

In carrying out the manufacture of carbon paper according to the presentinvention, a mix is prepared by Sttes atent C) a 3,065,099 Patented Nov.20, 1962 stirring finely divided wax into water which is preferablywarmed somewhat for the purpose. In addition, it is preferred to add aconventional emulsifying agent. Fatty acid soaps may be used which arederived by reaction between a fatty acid having 22 or less carbon atomsand an alkali metal such as sodium or potassium. Sulfurcontainingemulsifiers such as the alkyl sodium sulfonates, sodium glycerylmonolaurate sulfate and dioctyl sodium sulfosuccinate may be used. Thenon-ionic emulsifying agents such as the ethylene oxide polymers alsoprovide good results. A mixture of fatty acid and alkali has been foundmost suitable since it aids in the formation of a more perfectsuspension of the wax and Water and also tends to soften and plasticizethe waxy coating which ultimately results. However, a suitablesuspension may be obtained by continuous beating of the wax-waterdispersion. Suitable coloring matter is added to the mix, preferably byfirst dispersing the same in a quantity of water which is then mixedwith the wax-water dispersion. The Whole is then preferably passedthrough a ball or colloid mill to render the dispersion smooth anduniform.

When the coating mix is completed, it is spread evenly on a flexiblewater-resistant foundation by vat coating, spraying, airknife, reverseroll coating or the like. It is then heated to at least the fusiontemperature of the wax used to melt the wax and evaporate the water,forming a waxy colored layer which is transferable to an adjacentcontacting surface by pressure, but which is exceedingly dry, non-tackyand smudge-resistant.

Drying of the final sheet occurs preferably by heating to a temperaturein the area of the melting point of the usual vegetable and mineralWaxes employed in the transfer layer. This may be accomplished bypassing the coated sheet through a drying tunnel, drying loft or onheated rollers. To drive off the water, the heating time iscomparatively long in the loft method Where low temperatures are used,and comparatively short where the high temperatures of heated rollersare used. The tunel method of heating is therefore preferred in whichmedium temperatures in the range of 250 F. are employed and the dwelltime is just long enough to provide excellent results. In this way, thewax layer fuses to a smooth, clean surface.

Where paper is used as the foundation material, it should be sized orotherwise treated to render it Waterresistant. Conventional sizing bathsmay be used containing materials such as protein-formaldehyde,caseinformaldehyde, melamineformaldehyde and urea-formaldehydecondensates, acrylate and methacrylate polymers, polyvinyl alcohol, etc.Such materials may be incorporated in the make-up of the sheet by addingthem to the heaters, or otherwise applied in manners well-known to thosein the art. Also, unsized paper may be treated with a coating of ethylcellulose, vinyl resin or other synthetic polymer to render itwater-resistant.

The ingredients mentioned heretofore are present in the pigmentdispersion in about the following proportions:

Parts by weight Wax 8 Emulsifying agent (fatty acid and alkali) 10-20.Coloring matter 16- 32. Water Sufficient to provide of emulsifying agentused, but oleic acid and potassium hydroxide have been found to Workvery satisfactorily. In this connection it is noted that the alkalishould be present in sufficient amount to bring about proper suspensionin the water of all of the other ingredients, and to this end it ispreferred that the alkali be at least equal in weight to the fatty acidpresent.

The coloring matter may be any of various pigments or lakes dependingupon the hue desired and preferably is present in an amount equal toabout two to four times the weight of the wax present. In case it isdesired that the transfer layer have hectographic or copying propertiesso that the mark produced shall be usable as a master in a hectographicduplicating process, dyes soluble in alcohol or suitable duplicatingfluids may be substituted in whole or in part for the pigments or lakes.

While it is not essential, the character of the coating is frequentlyfound to be improved by adding a small amount of glycerine which acts asan additional softening agent.

In order that the invention may be more clearly understood, thefollowing description of a particular preferred coating composition isgiven by way of example but is not intended to be limiting upon theinvention.

Example Parts by weight Ouricoury wax 4 Microcrystalline petroleum wax(Be Square Wax) 4 Oleic acid 6 Potassium hydroxide 8 Glycerine 1 Water100 When the above-listed ingredients have been thoroughly intermixedand reduced to a smooth uniform consistency, preferably in a colloidmill, they are mixed with about an equal weight of a color mixture, forexample a 20% dispersion in water of a pigment (e.g. carbon black), alake, or a dye, and the whole composition is preferably milled togetherfor a brief period. The composition is then in condition to be spread ina thin layer on a foundation member according to the procedurehereinbefore recited. When the layer is dry, the result is a completedtransfer member whose coating is readily and easily transferred to acontacting sheet by Writing or typing pressure. Furthermore, the surfaceof the transfer coating is clean and non-tacky and does not tend tosmudge or offset in those areas where pressure is not applied. Thecoating will be found to be supported well up on the surface of thefoundation and will not be impregnated materially into the body of thefoundation.

The foregoing description should not be construed as being limited tothe specific materials named, the essential point of the discovery beingthat water-wax dispersion coatings may be applied to water-resistantfoundation sheets or ribbons in a simple and economical manner toprovide transfer media having excellent properties ofcleanliness-to-the-touch and smudge-proof images.

Any of the suitable conventional pressuretransferable waxes, pigments,emulsifying agents and foundation sheets may be used and are well-knownto the art.

Thus, variations and modifications may be made within the scope of theclaims and portions of the improvements may be used without others.

I claim:

1. A pressure-sensitive transfer medium comprising a substantiallywater-resistant foundation bearing a pressure-transferable coatingcomprising the heat fused residue of a water dispersion containing amajor amount by weight of water, a water-insoluble wax, an emulsifyingagent, and coloring matter.

.2. A pressure-sensitive transfer medium according to claim 1 in whichthe water-resistant foundation is sized paper.

3. A pressure-sensitive transfer medium according to claim 1 in whichthe water-resistant foundation is a plastic film.

4. A pressure-sensitive transfer medium according to claim 1 in whichthe emulsifying agent comprises a mix ture of a fatty acid and analkali.

References Cited in the file of this patent UNITED STATES PATENTS1,925,235 Dixon Sept. 5, 1933 1,950,982 Gookin et al Mar. 13, 19341,954,451 Lawrence Apr. 10, 1934 2,348,128 Groak May 2, 1944 2,606,775Newman Aug. 12, 1952 2,931,752 Newman Apr. 5, 1960

1. A PRESSURE-SENSITIVE TRANSFER MEDIUM COMPRISING A SUBSTANTIALLYWATER-RESISTANT FOUNDATION BEARING A PRESSURE-TRANSFERABLE COATINGCOMPRISING THE HEAT FUSED RESIDUE OF A WATER DISPERSION CONTAINING AMAJOR AMOUNT BY WEIGHT OF WATER, A WATER-INSOLUBLE WAX, AN EMULSIFYINGAGENT, AND COLORING MATTER.